What tests did you have before going on such generous doses of HC and now that you've decided to wean off?!
I fear you are reducing the dose too quickly.
A close friend with low saliva cortisol almost all day long actually likes 5-7,5mg HC plus several supplements better than 15mg HC originally suggested by her doctor.
She quickly gained 10+ lbs around the middle on the higher dose of HC.
I actually like her improved mental clarity better when she added pregnenolone--currently 65mg after followup testing.
If your cortisol levels were originally low and if followup tests while on HC looked encouraging why be afraid of it?
I agree that low cortisol might not be the only reason for fatigue. We typically see that in the heavy metal detox groups since HMs affect so many body processes.